Electro-Harmonix Tube EQ Analog Parametric/Shelving EQ Pedal It enhances your tone and gives you far more options than a regular EQ 2 filter sections offer tremendous tweakability The first offers passive high and low shelving functions corresponding to the Bass and Treble knobs on the pedal The second section is an active parametric bandpass filter that lets you set the center frequency and "Q "It's equipped with standard input and output jacks plus an expression pedal input that lets you sweep the center frequency of the bandpass filter for wah effects